A junction box (sometimes referred to as a battery interface center) simplifies vehicle electrical systems by organizing electrical components such as fuses, relays, electronic modules and branched circuits into a single housing. Wire harnesses connected to various vehicle electrical systems are routed into the junction box through connectors built into the junction box walls. Bus bars or circuit boards link the connectors to the various components housed in the junction box.
An example of a prior art junction box is illustrated in FIG. 1. Junction box 10 is molded from a non-conductive plastic. Conductive bus bars 32 are mounted on or formed integrally with a circuit board 2. Electrical components in the circuit board are electrically connected with various vehicle systems through bus bars 32 and terminals 3 which extend through the walls 4 of the junction box.
The circuit board and bus bars must be designed such that electrical paths defined by the bus bars and components do not cross. However, junction boxes are increasingly required to house an ever greater number of components, straining the ability of prior art bus bar and circuit board arrangements to accommodate the components in a single housing of limited size.
Attempts have been made to accommodate the increase in the number of components per junction box. U.S. Pat. No. 4,938,719 to Sawai et al discloses a junction box with multiple levels of insulated wires embedded in a block of insulating material. Contact terminals are inserted into the block to connect the various wires with the proper components. Drawbacks of this design are the complexity of the junction block and the limited layout options for the contact terminals throughout the various layers.
U.S. Pat. No. 5,223,676 to Yamamoto et al. discloses multiple layers of conductors embedded in an insulated board. A drawback of this arrangement is that the substrate must be manufactured with the conductors embedded within. As the number of components increases, the substrate becomes thicker and more difficult to make, and places a significant limit on the number of components that can be added to the junction box.
U.S. Pat. No. 5,306,181 to Monie et al. discloses a planar fuse panel where the conductive metal is selectively coated with an insulating layer to allow closer packaging of components without the electrical current crossing paths.
U.S. Pat. No. 5,434,749 to Nakayoma discloses a circuit board having a flexible printed circuit sheet through which the conductors pass. The ends of the conductors are bent up (terminal portions) or down (connection tabs) to pass through a circuit board and an insulation substrate to engage a bus bar connection pattern in the printed circuit board. This patent also discloses alternating stacked layers of circuit boards and insulation substrates to separate the overlapping bus bars.